This invention deals generally with latching mechanism for doors employed in pressure vessels. Such doors find use, for instance, in steam cookers, ink supply tanks, surgical instrument sterilizers, and pressurized airplane cabins. In the particular embodiment the invention relates to latching mechanism for doors utilized in pressure vessels of the type shown in Vischer U.S. Pat. No. 2,904,212 and in Vischer U.S. Pat. No. 3,409,164. These pressure vessels are used for food preparation in restaurants and institutional kitchens and employ a generally circular access door which is structurally warped about one axis. During use the door is positioned inside the pressure vessel, which has a circular access opening slightly smaller in diameter than the non warped diameter of the door. The door warp facilitates insertion of the door through the access opening, and after insertion through the access opening the door is stressed against an interior rim of the access opening to achieve an air tight seal. As the stressing takes place the door is flexed to remove the warp and assume the configuration of a spherical section of circular outline.
For opening or closing of doors of the type shown in the Vischer patents, the door is mounted on a support arm, which in turn is attached to the exterior of the pressure vessel along a moveable hinge line. This hinge line is moveable between a first point enabling door passage through the access opening and a second point enabling centering of the door within the access opening. During a typical door closing sequence the hinge line is initially in its first position, and the door is manually inserted through the access opening until it is inside the pressure vessel and clear of the rim of the access opening. Thereafter the door and its hinge line are shifted until door centering within the access opening is accomplished. From this centered position the door is pulled outwardly toward the door support arm, thereby contacting the rim of the access opening and commencing the above mentioned flexing sequence. Means are provided for securing the door in its sealed position.
For accomplishing the above mentioned door sealing action, there may be provided a camming assembly as shown in Vischer U.S. Pat. No. 2,904,212 or a worm and crank arrangement as shown in Vischer U.S. Pat. No. 3,409,164. The assembly of Vischer U.S. Pat. No. 2,904,212 is best applied to fairly small doors, because the available mechanical advantage for door flexing is rather small. The arrangement of Vischer U.S. Pat. No. 3,409,164 provides a much larger mechanical advantage and is therefore better suited for usage with larger doors. In this latter arrangement the available mechanical advantage depends upon the pitch of the worm and this may be selected to meet the particular application. Doors built in accordance with Vischer U.S. Pat. No. 3,409,164 necessarily require a fairly large amount of handle turning and therefore are not as fast to operate as doors build in accordance with Vischer U.S. Pat. No. 2,904,212.